QNAP
QNAP TS-873A vs Synology DS1821+: Eight Bays, Network Speed and Expansion
Eight bays and the same processor do not make these NAS systems interchangeable. Compare the network, memory, storage workflow and recovery plan as one system.
TS-873A starts with dual 2.5GbE and flexible PCIe expansion; DS1821+ starts with four Gigabit ports and ECC memory. Both use the Ryzen V1500B, but the network path, supported storage software and recovery workflow matter more than the shared CPU. Compare the complete system before adding memory or a faster adapter.
A photography studio outgrows its four-bay NAS, or a business needs room for a larger archive. Eight bays provide more layout choices, but the real decision is how people will use the storage and recover it. For these established models, also distinguish an upgrade to equipment you already own from a fresh purchase with several years of intended service.
The Hardware Differences That Change the Plan
| Feature | QNAP TS-873A-8G | Synology DS1821+ |
|---|---|---|
| Processor | Ryzen Embedded V1500B, four cores/eight threads, 2.2 GHz | Ryzen Embedded V1500B, four cores/eight threads, 2.2 GHz |
| Stock memory | 8 GB DDR4; ECC supported, not a promise of stock ECC | 4 GB DDR4 ECC |
| Official maximum memory | 64 GB | 32 GB |
| Built-in Ethernet | Two 2.5GbE ports | Four 1GbE ports |
| PCIe expansion | Two PCIe Gen 3 ×4 slots | Gen 3 ×8 physical slot with ×4 link |
| M.2 slots | Two M.2 2280 PCIe Gen 3 ×1 slots | Two M.2 2280 NVMe slots |
| Software decision | QTS or a supported QuTS hero deployment | DSM and supported packages |
Confirm the exact RAM, network card and drive list for the enclosure. A supported expansion slot is not a guarantee that any card will work. Treat the supplied memory configuration separately from the platform’s ECC capability.
Will Faster Ethernet Change the Working Day?
A large-file workflow can benefit from a faster path, but every section must fit. TS-873A offers 2.5GbE without an add-in network card; DS1821+ needs suitable expansion for a faster single Ethernet path. The computer, switch and cables must support the chosen rate too.
Four Gigabit interfaces do not automatically make one file transfer run at 4 Gb/s. Link aggregation can distribute suitable traffic across links, while SMB Multichannel has its own client, server and interface requirements. Neither should be assumed from the port count alone.
For one busy editor, test the actual file type and pool. For several users, test concurrent work rather than only one sequential copy. The slow NAS transfer guide helps identify whether the busy stage is the network, disks, CPU or application.
Eight Bays Do Not Remove Every Bottleneck
Storage, networking and recovery need separate plans.
01 A large-file transfer
Link rates are not file-copy benchmarksAdding ports does not automatically multiply the speed of one connection.
02 A recoverable library
RAID keeps service through some disk failuresIt is not an independent backup for deletion, malware or loss of the enclosure.
QTS, QuTS hero and DSM Are Workflow Choices
TS-873A supports QTS and an appropriate QuTS hero deployment. Choosing a different storage operating system is a planned migration, with its own memory, pool and compatibility requirements. It is not a harmless switch to flip on a populated NAS: preserve backups and follow the documented reinitialisation process where required.
DSM may suit a team already trained in Synology file services, snapshots and backup administration. Compare the required packages, permissions and recovery procedures rather than assuming one interface is universally easier.
More RAM can help an identified workload, such as several supported applications or virtual machines. It does not make a saturated Gigabit link faster. ECC is an additional integrity feature; it does not replace snapshots, backups or recovery testing. The NAS operating-system comparison gives the wider software context.
Eight Drives: Capacity, Reserve and a Restore
Eight bays provide layout choices, not eight drives of free space. As a simple equal-drive example, eight 12 TB disks provide 96 TB raw. A conventional RAID 6 layout leaves about 72 TB before formatting, metadata, snapshots and reserve. That arithmetic is not a guarantee of supported drive capacity or final reported TiB.
Leave room for normal growth and maintenance. A nearly full pool can make an expansion decision more urgent and recovery less convenient. Compare supported external expansion only for the exact model; avoid multiplying a headline disk capacity into a universal maximum system size.
RAID can keep service through some disk failures. It does not protect against every accidental deletion, compromised account, ransomware event or loss of the enclosure. Test recovery from an independent copy with realistic data and permissions.
Dual 2.5GbE and two PCIe slots offer a flexible starting point. Match RAM, software and expansion parts to the exact deployment.
Stock ECC memory and the DSM workflow may fit an existing team. Plan a supported network card if one Gigabit path is insufficient.
Existing Owner or New Buyer? Ask Different Questions
Already own one: measure the workload, check health and support status, and price a targeted network or memory upgrade against replacement. Keep a rollback and an independent backup before changing the storage layout.
Buying now: compare current eight-bay alternatives as well as these established models. Include software support, warranty, drives, network cards, switch ports and the recovery destination in the budget. Check current product pricing through the exact model links rather than relying on historical launch prices.
Choose the Platform Around the Complete Job
Shortlist TS-873A when its built-in 2.5GbE, expansion flexibility and supported QNAP workflow address the requirement. Shortlist DS1821+ when stock ECC and the supported DSM workflow fit the organisation. For either model, define the network, usable capacity and restore procedure before deciding that more bays alone solve the problem.
Frequently Asked Questions
Do these NAS systems use the same processor?
Yes. Both use the four-core, eight-thread Ryzen Embedded V1500B at 2.2 GHz. Other hardware, software and the actual workload still affect the result.
Does TS-873A include ECC memory as standard?
ECC is supported, but do not assume that the stock TS-873A-8G configuration contains ECC RAM. Verify the supplied module and supported upgrade. DS1821+ is specified with stock ECC memory.
Will four Gigabit ports make one copy four times faster?
Not automatically. Aggregation and SMB Multichannel have different requirements, and the computer, switch, protocol and workload must support the intended arrangement.
Can I use every M.2 slot as an SSD storage pool?
No universal rule applies. Check each platform’s supported role, drive compatibility and software. A slot described for cache does not automatically establish pool support.
Can I switch QTS to QuTS hero without planning a migration?
Do not assume so. Follow the supported model and software procedure, with independent backups and the required reinitialisation or data migration plan.
Does RAID 6 replace a backup?
No. It addresses a limited set of disk failures. Keep an independent recovery copy and test a restore of the data and permissions that matter.
